Authors:

A brief introduction to the brain-mind problem leads on to a survey of the neuronal structure of the cerebral cortex. It is proposed that the basic receptive units are the bundles or clusters of apical dendrites of the pyramidal cells of laminae V and III-II as described by Fleischhauer and Peters and their associates. There are up to 100 apical dendrites in these receptive units, named dendrons. Read More

Authors:

Flukes of cetaceans are capable of absorbing energy from ocean waves for propulsion. The extent of this energy absorption is demonstrated by considering the flukes of an immature fin whale, Balaenoptera physalus. In a fully developed seaway corresponding to a wind speed of 20 knots (around Beaufort force 5) and at a low swimming speed, of 2. Read More

Authors:

In the receptor-transducer model of pharmacological agonism, rejection of the traditional assumption that receptor molecules are in vast excess of transducer molecules permits the receptors to become distributed among unbound, bound and complexed states. Under these conditions, agonist affinities are liable to be overestimated when the method of irreversible receptor antagonism is used. Graphical tests have been developed to detect distribution, and these were applied to experimental data from the interaction between 5-HT and phenoxybenzamine on aortic tissue. Read More

Authors:

Division of Neurobiology, Medical School, University of Newcastle upon Tyne, U.K.

The responses to single electrical stimuli have been recorded from neurons in the brains of domestic chicks, by using an in vitro preparation consisting of a coronal slice taken from the forebrain. All slices were cut so that they contained the intermediate part of the medial hyperstriatum ventrale (IMHV). When such a slice is bathed in standard Krebs' solution there is no evidence that the excitation produced by a single stimulus can be transmitted more than 1 mm either towards or away from the IMHV. Read More

Authors:

Division of Neurobiology, Medical School, University of Newcastle upon Tyne, U.K.

The responses to local stimulation have been recorded from neurons in the intermediate part of the medial hyperstriatum ventrale (IMHV) of the domestic chick, by using an in vitro slice preparation. When the slice is bathed in gassed Krebs' solution, a single stimulus evokes a short-lasting diphasic response. The first phase is negative and lasts some 3 ms, whereas the second, positive phase is often of lower amplitude and usually persists for about 15 ms. Read More

Authors:

A series-parallel model of the kinetics of the voltage-gated sodium channel is described. It goes some way towards reconciling the time-courses of the gating and macroscopic sodium currents in the squid giant axon with the molecular structure of the channel. Read More

Authors:

A critical study has been made of the characteristics of the kinetic components of the sodium gating current in the squid giant axon, of which not less than five can be resolved. In addition to the principal fast component Ig2, there are two components of appreciable size that relax at an intermediate rate, Ig3 alpha and Ig 3 beta. Ig3 alpha has a fast rise, and is present over the whole range of negative test potentials. Read More

Authors:

ATP-sensitive K(+)-channel currents were recorded from isolated membrane patches and voltage-clamped CRI-G1 insulin-secreting cells. Internal Mg2+ ions inhibited ATP-K+ channels by a voltage-dependent block of the channel current and decrease of open-state probability. The run-down of ATP-K+ channel activity was also shown to be [Mg2+]i dependent, being almost abolished in Mg2(+)-free conditions. Read More

Authors:

Neutron diffraction has been used to determine the preferred orientation of the hydroxyapatite crystals at the lower front edge of the tibia. The bones are compared for two Neolithic Orkney tribes. At Isbister, a muscular tribe on a hilly site engaged in heavy uphill work, whereas a tribe at Quanterness lived on level ground. Read More

Authors:

Staining for motor endplates and chemical digestion of five major muscles of the domestic chicken shows that these confirm the short-fibre strap muscle paradigm. The individual fibres are spindle-shaped, terminating in gradually tapering ends. The motor endplates of the individual fibres align in cross-bands along the length of the fascicles. Read More

Authors:

The visual system can extract information about shape from the pattern of light and dark surface shading on an object. Very little is known about how this is accomplished. We have used a learning algorithm to construct a neural network model that computes the principal curvatures and orientation of elliptic paraboloids independently of the illumination direction. Read More

Authors:

Centre for Visual Sciences, Research School of Biological Sciences, Australian National University, Canberra, A.C.T.

Adopting principles learnt from insect vision we have constructed model of a general-purpose front-end visual system for motion detection that is designed to operate in parallel along each photoreceptor axis with only local connections. The model is also designed to assist electrophysiological analysis of visual processing because it puts the response to a moving scene into sets of template responses similar to the distribution of activity among different neurons. An earlier template model divided the visual image into the fields of adjacent receptors, measured as intensity or receptor modulation at small increments of time. Read More

Authors:

If a single ion channel record is observed in which two ion channels are never simultaneously open, then it is often of interest to know whether the observations indeed arose from the activity of only one ion channel. This question can be answered if it is possible to calculate the distribution of the duration of runs of single openings in a membrane patch that contains two active channels. If the observed run of single openings is much longer than that expected for a patch with two channels it is likely that only one channel was active. Read More

Authors:

The hypothesis that calcium release from the sarcoplasmic reticulum in cardiac muscle is induced by rises in free cytosolic calcium (Fabiato 1983, Am. J. Physiol 245) allows the possibility that the release could be at least partly regenerative. Read More

Authors:

Department of Theoretical Physics, Schuster Laboratory, University of Manchester, U.K.

Computer simulations in which selection acts on a quantitative character show that the randomness of mutations can contribute significantly to evolutionary divergence between populations. In different populations, different advantageous mutations occur, and are selected to fixation, so that the populations diverge even when they are initially identical, and are subject to identical selection. This stochastic process is distinct from random genetic drift. Read More

Authors:

Muscular Dystrophy Group Research Laboratories, Newcastle General Hospital, U.K.

Immunolabelling with a 5 nm gold probe was used to localize dystrophin at the ultrastructural level in human muscle. The primary antibody was monoclonal, raised against a segment (amino acids 1181-1388) from the rod domain of dystrophin. The antibody (Dy4/6D3) is specific for dystrophin and shows no immunoreactivity with any protein from mdx mouse muscle or from patients with a gene deletion spanning part of the molecule recognized by the antibody (Nicholson et al. Read More

Authors:

We have used the calcium indicator dye arsenazo III, together with a photodiode array, to record intracellular calcium changes simultaneously from all regions of individual guinea pig cerebellar Purkinje cells in slices. The optical signals, recorded with millisecond time resolution, are good indicators of calcium-dependent electrical events. For many cells the sensitivity of the recordings was high enough to detect signals from each array element without averaging. Read More

Authors:

Department of Theoretical Physics, Schuster Laboratory, University of Manchester, U.K.

We describe a computer model that stimulates a combination of stabilizing and frequency-dependent selection acting on a quantitative character determined by several loci. The results correspond to many features of natural variations at both the phenotypic and genotypic levels. The model is robust, and its results are not strongly dependent either on the nature and shape of the function describing the stabilizing selection, or on the precise form of frequency dependence, except near the extrema. Read More

Authors:

Phylogenies based on morphology vary considerably in their quality: some are robust and explicit with little conflict in the data set, whereas others are far more tenuous, with much conflict and many possible alternatives. The main primary reasons for untrue or inexplicit morphological phylogenies are: not enough characters developed between branching points, uncertain character polarity, poorly differentiated character states, homoplasy caused by parallelism or reversal, and extinction, which may remove species entirely from consideration and can make originally conflicting data sets misleadingly compatible, increasing congruence at the expense of truth. Extinction differs from other confounding factors in not being apparent either in the data set or in subsequent analysis. Read More

Authors:

The actions of the polychlorocycloalkane insecticide heptachlor, and its epoxide metabolite, were examined on GABA receptors in insects and vertebrates. Electrophysiological experiments on the cell body of the cockroach (Periplaneta americana) fast coxal depressor motor neuron (Df), and GABA-activated 36Cl- uptake experiments on microsacs prepared from cockroach ventral nerve cords showed that both heptachlor and heptachlor epoxide blocked functional GABA receptors. The block appeared to be non-competitive and was voltage-independent over the membrane potential range -75 mV to -110 mV. Read More

Authors:

Department of Physiology, College of Medicine, Seoul National University, Korea.

To investigate the underlying ionic mechanism of the late plateau phase of the action potential in rabbit atrium the whole-cell patch-clamp technique with intracellular perfusion was used. We recorded the inward current during repolarizations following a brief 2 ms depolarizing pulse to +40 mV from a holding potential of between -70 and -80 mV. The development of this current coincides with the onset of the late plateau phase of the action potential. Read More

Authors:

Perceptual segregation of visual textures has been attributed to certain features ('textons') such as (elongated) blobs of given size and orientation, line crossings, and line ends. Differences in the spatial distribution of these features were assumed to be detected pre-attentively and to provide the instantaneous impression of segregating texture areas and of borders between them. This paper questions the validity of this general view and, in particular, the role of some of these features in texture discrimination. Read More

Authors:

Neurobiology Research Centre, University of Sydney, New South Wales, Australia.

A model of the secretion of a quantum at a release site is proposed in which, following the influx of calcium ions, synaptic vesicles are made available for release by the activation of kappa phosphorylation steps with rate alpha. At any time during this process the vesicles may become unavailable for secretion at rate gamma. On completion of the kappa phosphorylation steps the vesicles participate in the formation of a fusion pore with the terminal membrane to give exocytosis at rate delta. Read More

Authors:

Eggs of the ascidian Ciona intestinalis were loaded with the calcium indicator fura-2 via whole-cell clamp electrodes and changes in cytoplasmic calcium and cell currents were monitored during fertilization either in separate eggs or simultaneously in the same egg. The first indication of egg activation was the fertilization current; which reached peak values around 1 nA after 30 s. A wave of elevated calcium was detectable between 5 s and 30 s (mean = 21 s) after the start of the fertilization current. Read More

Authors:

The pigmentation pattern of Alligator mississippiensis was examined. The number of white stripes on the dorsal side of embryos (stages 21-28) and hatchlings from eggs incubated at 30 degrees C (100% females) and 33 degrees C (100% males) was recorded. Total length, nape-rump length and tail length were recorded for each embryo and hatchling. Read More

Authors:

In primates the retina is connected with different targets in the brain via several parallel pathways, the largest of which is that going to the lateral geniculate nucleus of the thalamus and thence to the striate cortex, the geniculo-striate pathway. When this route is damaged in man, apparent blindness in a corresponding part of the visual field occurs, despite the integrity of the other parallel pathways. In animals, it has been demonstrated by conventional behavioural forced-choice techniques that extrastriate routes can sustain a variety of visual discriminations. Read More

Authors:

Some computational theories of motion perception assume that the first stage en route to this perception is the local estimate of image velocity. However, this assumption is not supported by data from the primary visual cortex. Its motion sensitive cells are not selective to velocity, but rather are directionally selective and tuned to spatio-temporal frequencies. Read More

Authors:

Voltage-activated currents were studied in whole-cell patch-clamped rat neocortical neurons growing in culture and treated with tunicamycin (TU), an inhibitor of protein N-glycosylation. The size of the Na+ current decreased progressively in the presence of TU (1-2 microM). This decrease was faster in growing 5-14 day-old neurons (to ca. Read More

Authors:

Centre for Visual Sciences, Research School of Biological Sciences, Australian National University, Canberra ACT.

Simple stimulus patterns, in this case visual, are represented by spatiotemporal Boolean functions that can be summarized in a 4 x 4 look-up table of 16 templates behind each sensory neuron. These groups of templates correspond to groups of neurons in columns behind each receptor. They abstract specific combinations of input in simple combinations and include two successive states in time. Read More

Authors:

Medical Research Council Laboratory of Molecular Biology, Cambridge, U.K.

The hallmark of the antibody response to antigenic challenge is its remarkable specificity. In his Croonian Lecture in 1905, Ehrlich recognized it as a biological puzzle, but considered it inconceivable that animals could produce substances capable of specific recognition of toxins that the species had never encountered before. It took the largest part of the following 70 years to begin to understand the chemical base of the biological puzzle. Read More

Authors:

Membrane currents were recorded in voltage-clamped oocytes of Xenopus laevis in response to voltage steps. We describe results obtained in oocytes obtained from one donor frog, which showed an unusually large outward current upon depolarization. Measurements of reversal potentials of tail currents in solutions of different K+ concentration indicated that this current is carried largely by K+ ions. Read More

Authors:

Department of Theoretical Physics, Schuster Laboratory, University of Manchester, U.K.

The effect, on the evolution of resistance, of alternating two unrelated insecticides in space or in time (or both) is studied. Transient polymorphism is shown to occur under certain conditions of mating, selection and migration. In some situations, the transient polymorphism can show a sharp decline before the alleles recover to fixation. Read More

Authors:

Injection of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) into the animal pole of Xenopus oocytes induced membrane depolarization due to the internal mobilization of calcium, which activates a chloride conductance. Repetitive injections of Ins(1,4,5)P3 results in desensitization probably as a result of depletion of the internal store of calcium. Desensitization was restricted to the region surrounding the site of injection. Read More

Authors:

A polyclonal, monospecific antiserum raised against a nicotinic acetylcholine receptor protein affinity-purified from insect nervous tissue, was employed to demonstrate the localization of antigenic sites in the neuropile of the terminal (sixth) abdominal ganglion of the cockroach Periplaneta americana. In agreement with previously published autoradiographic mapping of specific [125I]alpha-bungarotoxin binding sites, specific areas of the central neuropile of this ganglion were densely stained, but not the cercal afferent axons. No staining was detected corresponding to the dense, peripheral, partly non-specific binding of alpha-bungarotoxin seen in autoradiographs of the same tissue. Read More

Authors:

Action potentials were recorded from single cells isolated from guinea-pig ventricular muscle. Contraction was measured with an optical technique. Tail currents thought to be activated by cytosolic calcium were recorded when action potentials were interrupted by application of a voltage-clamp. Read More

Authors:

Synapses that can be strengthened in temporary and persistent manners by two separate mechanisms are shown to have powerful advantages in neural networks that perform auto-associative recall and recognition. A multiplicative relation between the two weights allows the same set of connections to be used in a closely interactive way for short-term and long-term memory. Algorithms and simulations are described for the storage, consolidation and recall of patterns that have been presented only once to a network. Read More

Authors:

Marine Sciences Research Center, State University of New York, Stony Brook 11794-5000.

We present a diffusion-competition model to describe the interaction between the externally introduced grey squirrel and the indigenous red squirrel in Britain. We estimate the model parameters from field data. Solution of the model predicts waves of grey squirrel invasion with speed of invasion typical of that observed in the field. Read More

Authors:

It is well established that exposure of oxyhaemoglobin to ionizing radiation results in remarkably selective electron addition to the (FeO2) unit, giving a novel species, (FeO2)-, in which the extra electron is largely localized on iron and dioxygen. This work has now been extended to haemoglobin (Hb.) Iwate. Read More

Authors:

School of Mathematical and Physical Sciences, Murdoch University, Western Australia.

Membrane patches usually contain several ion channels of a given type. However, most of the stochastic modelling on which data analysis (in particular, estimation of kinetic constants) is currently based, relates to a single channel rather than to multiple channels. Attempts to circumvent this problem experimentally by recording under conditions where channel activity is low are restrictive and can introduce bias; moreover, possibly important information on how multichannel systems behave will be missed. Read More

Authors:

Department of Biological Sciences, University of California, Santa Barbara 93106.

RNA from Cyanophora paradoxa was separated into cytoplasmic and cyanellar fractions by using a combination of subcellular fractionation and oligo-dT chromatography. In vitro translation of the separated cytoplasmic and cyanellar RNAs in a rabbit reticulocyte lysate system in the presence of [35S]methionine resulted in the incorporation of radiolabel into electrophoretically distinct sets of polypeptides. Monospecific and polyspecific antibodies that react with cyanellar polypeptides were used to probe the in vitro translation products by indirect immunoprecipitation by using Staphylococcus protein A conjugated to Sepharose beads. Read More

Authors:

Department of Biological Sciences, University of California, Santa Barbara 93106.

Cycloheximide and chloroamphenicol, specific inhibitors of protein translation in the cytoplasmic and cyanellar compartments, respectively, of Cyanophora paradoxa, have been employed in 30 min pulse-labelling experiments by using [NaH-14C]O3 to label total cell proteins in vivo. Cyanellae purified from host cell lysates were separated into soluble and thylakoid fractions and analysed by one- and two-dimensional polyacrylamide gel electrophoresis (PAGE) to determine the distribution of radioactivity in the cyanellar polypeptides. Analysis of the autoradiograms of electrophoretically resolved proteins of the cyanellae indicates that about 70% of the total number of cyanellar proteins visualized in the controls are synthesized on cytoplasmic ribosomes. Read More

Authors:

Department of Biological Sciences, University of California, Santa Barbara 93106.

Based on polypeptide separation, protein purification and immunoblotting techniques using heterologous antibodies, we have been able to identify several photosynthetically important polypeptide components of the cyanellae of Cyanophora paradoxa. Cytochrome c-552 and ferredoxin have been purified to electrophoretic homogeneity and exhibit apparent molecular masses of 10.5 and 9. Read More

Authors:

Department of Neurology, Yale University School of Medicine, New Haven, Connecticut.

Immuno-electron microscopic localization of sodium channels at nodes of Ranvier within adult optic nerve was demonstrated with polyclonal antibody 7493. The 7493 antisera, which is directed against purified sodium channels from rat brain, recognizes a 260 kDa protein in immunoblots of the crude glycoprotein fraction from adult rat optic nerve. Intense immunoreactivity with 7493 antisera was observed at nodes of Ranvier. Read More

Authors:

Center for Automation Research, University of Maryland, College Park 20742.

Shading (variations of image intensity) provides an important cue for understanding the shape of three-dimensional surfaces from monocular views. On the other hand, texture (distribution of discontinuities on the surface) is a strong cue for recovering surface orientation by using monocular images. But given the image of an object or scene, what technique should we use to recover the shape of what is image? Resolution of shape from shading requires knowledge of the reflectance of the imaged surface and, usually, the fact that it is smooth (i. Read More

Authors:

'Horor autotoxicus', as it was termed by Erhlich, is a rare clinical event despite the genetic potential of every individual to mount immune responses to self-antigens. This can be explained by the fact that the developing immune system learns to recognize self-antigens and to tolerate them. The key to autoimmunity therefore lies in unravelling the mechanisms of self-tolerance. Read More

Authors:

Jerry Lewis Neuromuscular Research Center, UCLA School of Medicine 90024.

Periodic oscillations in miniature endplate potential (MEPP) frequency have been described at the frog neuromuscular junction. It is assumed that the periodic oscillations in MEPP frequency reflect cytosolic oscillations in intracellular Ca2+ concentration. In the course of a study related to describing the differences between weak and strong neuromuscular junctions by using the post-tetanic potentiation of MEPP frequency, we noted periodic oscillations in MEPP frequency in the first few minutes after a tetanus. Read More

What are PubFacts Points?
PubFacts points are rewards to PubFacts members, which allow you to better promote your profile and articles throughout PubFacts.com

How do I earn PubFacts Points?
Each member is given 50 PubFacts points upon signing up. You can earn additional points by completing 100% of your profile, creating and participating in discussions, and sharing other members research.

What can I do with PubFacts Points?
Currently, you can use PubFacts Points to promote and increase readership of your articles.